It is generally known to provide water-tight bulkheads that partition the interior space within the hull of a ship into separate water-tight compartments. Such water-tight bulkheads or partitions of the ship's interior volume provide increased safety in the event of a hull leak, hull breach, capsizing or other flooding event. Namely, if water is flooding into one of the partitioned compartments of the ship, it is intended to confine the water to the affected compartment, and prevent the flooding of water beyond the bulkheads into other water-tight compartments. For that purpose, any penetrations through the bulkheads, for example a through-hole through which a rotating shaft extends, must be sealed with a suitable seal arrangement, especially on the occurrence of a flooding event.
Thus, wherever a rotating shaft (such as a drive shaft extending from an engine to a propeller of the ship, or some other power train shaft) must penetrate through such a partition bulkhead, it is known to provide a seal around the shaft, which seal allows the shaft to rotate and also allows some radial motion or vibration of the shaft, while nonetheless establishing a water-tight seal around the shaft in the opening of the bulkhead through which the shaft extends. Various configurations of such shaft seals are known. In a simple seal arrangement, seal rings such as rubber or polymer seal rings are arranged around the shaft and contact the shaft to establish a seal, while allowing the shaft to rotate. However, such shaft seals all suffer certain disadvantages and problems. For example, the frictional rubbing contact of the shaft with the seal rings causes considerable wear of the seal rings, and also causes noise which is transmitted through the shaft seal into the bulkhead and the rest of the ship structure. The frictional rubbing contact also causes the generation of heat, which accelerates the wear and aging breakdown of the seal rings and/or the shaft. Even though some types of known shaft seals are adjustable, i.e. the position of the seal rings can be radially adjusted, it is nonetheless difficult to compensate or adapt to the arising radial shaft motion, and only a very limited range of radial motion can be accommodated. That causes further wear of the shaft seal.
It is desired to reduce the wear, reduce the noise generation, increase the operational longevity, reduce the maintenance, avoid the further disadvantages of known shaft seals, and still provide effective sealing when the need for providing a water-tight seal of the bulkhead arises.